Domestic hot water too hot

Baytree_2

Hi,

I have a Glow Worm Hideaway 60BF floor standing boiler, which is less than 10 years old. The problem I have is that even after replacing the thermostat on the boiler (twice), the water is still getting too hot. If I turn it down to near minimum, we get no hot water at all and all the radiators stay cold. But if I turn it even slightly higher, the radiators quickly warm up and after several hours the water in the taps become too hot. Not quite too hot to put your hands under, but you wouldn't want to leave them there for long!

The strange thing is that our heating switches off at 10:30 pm, yet at 6:30 the following morning (before the heating comes on again), the water is still extremely hot. It's a gravity fed system, but I cannot understand why it doesn't cool down overnight - it never used to stay hot all the time.

Does anyone have any theories before I call in a heating engineer?

Many thanks.

bengraves38

Hi, I take it you have a tank fed system.

I am guessing one reason the water will not turn down is you are adjusting the wrong stat? If there is one try adjusting the stat on the side of the hw storage tank?

As for the hw still being hot in the morning, have you noticed your electric bills are high?!?! The reason i ask is because a possible cause for the water still being hot in the morning is that there may be an immersion heater in the HW tank keeping the temprature up overnight.

Let me know if this is any help and add some piccies and i may be able to help further.

Ben

LittleMissAspie

I thought all hot water systems were like this. My hot taps start out cold, then go through a nice warm period, then get scorching. If I haven't finished rinsing my face I have to switch to the cold tap, the hot water is too hot.

Baytree_2

bengraves38 wrote: »

Hi, I take it you have a tank fed system.

I am guessing one reason the water will not turn down is you are adjusting the wrong stat? If there is one try adjusting the stat on the side of the hw storage tank?

As for the hw still being hot in the morning, have you noticed your electric bills are high?!?! The reason i ask is because a possible cause for the water still being hot in the morning is that there may be an immersion heater in the HW tank keeping the temprature up overnight.

Let me know if this is any help and add some piccies and i may be able to help further.

Ben

Hi Ben,

No, it's a very simple system with no thermostat on the hot water cylinder and although we do have a separate immersion heater, it's rarely used and is currently switched off.

No, the only thermostat (apart from the room thermostat of course) is on the boiler itself. I'm pretty sure we used to set on the half way position for maximum efficiency, but now it needs to be much lower.

I was wondering if it is possible to get an air lock in the boiler, around the area the thermostat takes it's reading? This would lead to that part of the boiler not getting hot enough to activate the switch.

It's now quite late and the heating has been switched off for the past 2 hours and the pipes leading up in the direction of the cylinder are cold. I've tried to 'catch it out' by checking if the boiler is firing during the night when it is supposed to be switched off, but without success. So maybe the cylinder is just very efficient at retaining heat?

Is there anything else in a boiler, other than the thermostat, that could be causing the domestic water to get too hot? Could the pilot light be too big or could a valve not be closing properly? Any suggestions would be welcomed.

Many thanks,


John

Baytree_2

LittleMissAspie wrote: »

I thought all hot water systems were like this. My hot taps start out cold, then go through a nice warm period, then get scorching. If I haven't finished rinsing my face I have to switch to the cold tap, the hot water is too hot.

It's the same here, but I don't think the water should be so hot you can't hold your hands under the tap, which is why I posted the question. I suspect we are burning way too much gas.

Many thanks,


John

craig777

Baytree wrote: »

I don't think the water should be so hot you can't hold your hands under the tap

This is pretty normal from my experience, if you have no seperate control over the DHW.

My old heating system was like this, my parents is like this and my works heating system is like this - I could easily make a cup of coffee that would be too hot to drink from the taps at my work!

bengraves38

Hi John,

Am i correct in thinking that when you have ch on you have hw on and vice versa or do you have seperate controlls for each?

I really cant understand why you do not have a cylinder stat for your hw (how would the boiler know when it was up to temp?)

There has to be a simple explanation for this if it used to work ok? As you mentioned you may ahve a very well insulated cylinder, which would go someway to explaining the water still being so hot in the morning.
I had a flat that was empty for a while that had an amazingly well insulated cylinder. We had the hw on one weekend and i called round mid week (tue/wed)to find the hw was still luke warm!

Any way back on topic it could be that you have a second stat in your boiler that you cannot get to? This could be causing the problem?

Just had a look at this website it does not seem u have more than one stat.
http://www.glow-wormorders.co.uk/manuals/pdf/Boilers/Hideaway60BF_UIS.pdf

What part of the stat have you replaced? Is it the controll knob or the actual capiliary sensor part, or both?

Do you have the courage to follow the electrical trouble shooting guide on page 21?:D

Ben

latecomer

Baytree wrote: »

could a valve not be closing properly?

thats something thats definitely worth checking out. If the valve which diverts water to the tank is stuck open then it will always be on while the central heating is on. If you can get access to it then check that when you turn the thermostat on the tank down that it closes and the pipe to the tank cools down (might take a while).

robv_3

Has the Phial been replaced?

On a side note would recommend you think about getting the system converted to fully pumped. Will give you more control over hot water and heating.

Baytree_2

craig777 wrote: »

This is pretty normal from my experience, if you have no seperate control over the DHW.

My old heating system was like this, my parents is like this and my works heating system is like this - I could easily make a cup of coffee that would be too hot to drink from the taps at my work!

Thanks - maybe it's just normal, but my last gas bill wasn't!

Baytree_2

bengraves38 wrote: »

Hi John,

Am i correct in thinking that when you have ch on you have hw on and vice versa or do you have seperate controlls for each?

I really cant understand why you do not have a cylinder stat for your hw (how would the boiler know when it was up to temp?)

There has to be a simple explanation for this if it used to work ok? As you mentioned you may ahve a very well insulated cylinder, which would go someway to explaining the water still being so hot in the morning.
I had a flat that was empty for a while that had an amazingly well insulated cylinder. We had the hw on one weekend and i called round mid week (tue/wed)to find the hw was still luke warm!

Any way back on topic it could be that you have a second stat in your boiler that you cannot get to? This could be causing the problem?

Just had a look at this website it does not seem u have more than one stat.
http://www.glow-wormorders.co.uk/manuals/pdf/Boilers/Hideaway60BF_UIS.pdf

What part of the stat have you replaced? Is it the controll knob or the actual capiliary sensor part, or both?

Do you have the courage to follow the electrical trouble shooting guide on page 21?:D

Ben

Hi Ben,

Yes, you are correct in that both CH and HW are on at the same time. But there is definitely no thermostat on the cylinder. I assumed the temperature of the water in the boiler would be controlled by the thermostat in the boiler, otherwise what purpose does it serve?

The thermostat and capillary/phial come as a complete unit, so both have been replaced (twice!).

There is something that I now ought to share with you, because it might explain why there was a 'before' and 'after'. The central heating system was originally installed by Mr Bodge who lived in the house before us. Unfortunately his pipework wasn't brilliant and whenever the system is drained we can end up with an air lock under the bathroom floor, which leaves us with no domestic hot water. I have cleared this in the past by draining and re-filling the system very slowly, but it doesn't always work at the first attempt.

Anyway, the last time I tried it I used a different tactic, following advice from a plumber. I withdrew the phial from the boiler, allowing the water to boil (loudly!), thus forcing the air from the system. It was only after this that the water became too hot and I assumed I had put the phial back in too quickly and somehow blown it. However, 2 thermostats and phials later, it is quite possible the simple reason for the water being so hot now is that this is the first time the system has been air free.

The cylinder, by the way is in quite a warm part of the house, away from any outside rooms, so it's possible it is simply holding the heat a long time.

So, now I have given the full background, does everyone think the boiler is functioning normally?

Also, does anyone know how easy it would be to fit a cylnder thermostat and can you buy wireless ones? Do I need power by the cylinder or is it near the boiler? Or can't it be done with a gravity-fed system?

I don't mind electrical work, but will leave gas to the professionals, of course!

Many thanks,


John